The aim of this project is to study the molecular events leading to the establishment of herpes simplex virus latent infections in the nervous systems of experimentally infected mice and of humans. The viral genome has been found in an integrated state in the trigeminal ganglion DNA of latently infected mice and various regions of DNA homology between viral and host (mouse and human) have been cloned from the mouse genome. Their possible involvement as preintegration sites is being studied. Viral DNA sequences have been found in ganglia of normal humans and in situ hybridization techniques have been used to detect the presence of viral transcripts. The gene coding for one of the major antigenic determinants in the virus surface has been precisely mapped and its cloning in an expression plasmid is being attempted.